feat: add complexity metrics for Objective-C (#1923)

[carlos-alm]

Summary

Progress on #1923 — adds objc complexity/Halstead support (tier 2).

tree-sitter-objc extends tree-sitter-c: if/else/for/while/switch/case/logical-operator/conditional-expression node kinds are byte-identical to plain C (confirmed by parsing sample ObjC control flow and inspecting the S-expression), including the same else_clause wrapper (Pattern A). Wires COMPLEXITY_RULES/HALSTEAD_RULES (TS) and lang_rules()/halstead_rules() (native) for objc, extending C's rule shape with:

• method_definition (the -/+ method body) added to functionNodes alongside function_definition
• catch_clause (from @try/@catch/@finally) treated as a branch/nesting node, the same treatment C++'s catch_clause already gets
• message_expression/selector_expression treated as compound Halstead operators, mirroring call_expression

Also fixes a native/WASM divergence this surfaced: the native ObjC extractor's handle_method ran complexity/CFG analysis unconditionally on both method_declaration (an @interface/@protocol signature, which never has a body) and method_definition, producing a spurious trivial complexity entry (cognitive 0, cyclomatic 1) for every interface declaration that duplicated the real method_definition entry under the same dotted name. Gated both on actual body presence and set bodyless accordingly; ported the same explicit bodyless signal to the TS/WASM extractor for defense-in-depth (its hasFuncBody skip logic otherwise relies on an endLine > line heuristic that a multi-line bodyless signature could slip past).

Verification

• npm run lint — clean
• npm test — 267/267 test files, 4335 passed, 30 skipped, 2 todo
• cargo test --lib (crates/codegraph-core) — 707/707 passed
• Native and WASM engines produce byte-identical codegraph complexity --health --json output on a hand-built fixture covering if/else-if/else, classic and fast-enumeration for loops, switch/case, @try/@catch/@finally, ternary, and message sends.

Remaining scope on #1923

Tier 1 (c, cpp, kotlin, swift, scala, bash) and CUDA were already done. Dart is blocked on #2182 (grammar structural issue) — do not attempt until that's fixed. Remaining unattempted: zig, haskell, ocaml, ocaml-interface, fsharp, fsharp-signature, gleam, clojure, julia, r, erlang, solidity, groovy, verilog.

Test plan

• npm run lint
• npm test
• cargo test --lib in crates/codegraph-core
• Native vs WASM diff on a hand-built ObjC fixture (identical output)

[greptile-apps]

Greptile Summary

Adds Objective-C complexity, Halstead, LOC, and maintainability metrics across the native and WASM analysis paths while preventing bodyless method declarations from receiving spurious complexity and CFG results.

• Adds mirrored Objective-C complexity and Halstead rule sets in Rust and TypeScript.
• Registers Objective-C for complexity, Halstead, and C-style LOC handling.
• Marks method declarations as bodyless and gates native complexity/CFG generation on an actual method body.
• Adds Objective-C control-flow and native/WASM parity tests.

Confidence Score: 5/5

The PR appears safe to merge, with native and WASM Objective-C metric behavior consistently wired and no actionable defect identified.

The mirrored rule sets classify the covered Objective-C constructs consistently, and explicit body detection prevents declaration-only methods from receiving complexity or CFG results.

Important Files Changed

Filename	Overview
crates/codegraph-core/src/ast_analysis/complexity.rs	Adds native Objective-C complexity, Halstead, and LOC rules with focused control-flow tests.
crates/codegraph-core/src/extractors/objc.rs	Gates native method metrics and CFG on body presence and records explicit bodyless state.
src/ast-analysis/rules/c.ts	Adds TypeScript Objective-C complexity and Halstead rules mirroring the native implementation.
src/ast-analysis/rules/index.ts	Registers Objective-C in the WASM complexity and Halstead rule maps.
src/extractors/objc.ts	Adds explicit bodyless signaling so declaration signatures are excluded from downstream analysis.
tests/unit/complexity.test.ts	Covers Objective-C methods, control flow, exception handling, Halstead output, and DFS/visitor parity.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart LR
  Source["Objective-C source"] --> Parse["tree-sitter-objc"]
  Parse --> Native["Native Rust extractor"]
  Parse --> Wasm["TypeScript/WASM extractor"]
  Native --> BodyCheck["Detect compound_statement"]
  Wasm --> Bodyless["Set explicit bodyless flag"]
  BodyCheck --> Metrics["Complexity + Halstead + LOC + MI"]
  BodyCheck --> CFG["CFG"]
  Bodyless --> Visitor["Shared analysis visitors"]
  Visitor --> Metrics
  Metrics --> Definition["Attach results to bodied definitions"]
  CFG --> Definition

Loading

_{Reviews (1): Last reviewed commit: "feat: add complexity metrics for Objecti..." | Re-trigger Greptile}

[github-actions]

Codegraph Impact Analysis

1 functions changed → 4 callers affected across 3 files

• handleMethodDecl in src/extractors/objc.ts:199 (4 transitive callers)

[carlos-alm]

Thanks for the review — 5/5 confidence, no actionable defects, nothing further to address here.